_Mercator and his Successors._--Of Gerhard Kremer (1512-1594) the earliest works are a map of Palestine (1537), a map of the world on a double heart-shaped projection (1525), and a topographical map of Flanders based upon his own surveys (1540), a pair of globes (1541, diam. 120 mm.), and a large map of Europe which has been praised deservedly for its accuracy (1554). He is best known by his marine chart (1569) and his atlas. The projection of the former may have been suggested by a note by W. Pirkheimer in his edition of Ptolemy (1525). Mercator constructed it graphically, the mathematical principles underlying it being first explained by E. Wright (1594). The "Atlas" was only published after Mercator's death, in 1595. It only contained nine maps, but after the plates had been sold to Jodocus (Jesse) Hondius the number of maps was rapidly increased, although Mercator's name was retained. Mercator's maps are carefully engraved on copper. Latin letters are used throughout; the miniatures of older maps are superseded by symbols, and in the better-known countries the maps are fairly correct, but they fail lamentably when we follow their author into regions--the successful delineation of which depends upon a critical combination of imperfect information. Even before Mercator's death, Antwerp and Amsterdam had become great centres of cartographic activity, and they maintained their pre-eminence until the beginning of the 18th century. Abraham Ortelius (1527-1592), of Antwerp, a man of culture and enterprise, but not a scientific cartographer, published the first edition of his _Theatrum orbis terrarum_ in 1570. It then contained 53 maps, by various authors. By 1595 the number of maps had increased to 119, including a _Parergon_ or supplement of 12 maps illustrating ancient history. In 1578 was published the _Speculum orbis terrarum_ of Gerard de Jude or de Judaeis. Lucas Janszon Waghenaer (Aurigarius) of Enkhuizen published the first edition of his _Spiegel der Zeevaart_ (Mariners' Mirror) at Leiden in 1585. It was the first collection of marine maps, lived through many editions, was issued in several languages and became known as _Charettier_ and _Waggoner_. In the same year Adrian Gerritsz published a valuable _Paskaarte_ of the European Sea. Ten years afterwards, in 1595, W. Barentszoon published a marine atlas of the Mediterranean, the major axis of which he reduced to 42 degrees. Jodocus Hondius has already been referred to as the purchaser of Mercator's plates. The business founded by him about 1602 was continued by his sons and his son-in-law, Jan Janszon (Jansonius) and others. By 1653 this firm had already produced atlases including 451 charts. Willem Janszon, the father of Hondius's partner, published a collection of charts (1608), to which he gave the title of _Het Licht der Zeevaart_ (the seaman's light). Another cartographic publishing firm was established at Amsterdam in 1612 by Willem Janszon Blaeu (1571-1638), a friend of Tycho